1. Field of the Invention
This invention relates to a novel anti-bacterial agent and, more particularly, this invention relates to 2,3,5,8-tetrahydrofuro- and 5,8-dihydrofuro[3,2-b]-1,8-naphthyridine compounds of the formula (I) ##STR2## wherein R.sup.1 represents an alkyl group having 1 to 6 carbon atoms and M represents a hydrogen atom, an alkali metal or an alkaline earth metal, having excellent anti-bacterial activity against both the gram-negative and gram-positive bacteria.
2. Description of the Prior Art
The compound of this invention has excellent anti-bacterial activity against gram-negative and gram-positive bacteria and its activity is superior to oxolinic acid (5-ethyl-5,8-dihydro-8-oxo-1,3-dioxolo[4,5-g]quinoline-7-carboxylic acid) which has a chemical structure similar to the compound of this invention and which is known as an excellent anti-bacterial agent described in Japanese Patent Publication No. 5666/1967 and J. Med. Chem., 11 160 (1968). Also, its activity is believed stronger than that of 5-ethyl-2,3,5,8-tetrahydro-8-oxofuro[2,3-g]quinoline-7-carboxylic acid which is known to have anti-bacterial activity equivalent to oxolinic acid as described in Chemical Abstracts, 76, p. 72499, U.S. Pat. No. 3,773,769, German Pat. (OLS) No. 2,030,899, Japanese patent application (OPI) No. 1081/1972.